JP2789339B2 - Ink jet recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ink jet recording apparatus.
The present invention relates to an ink jet recording apparatus having a discharge unit for removing bubbles generated in an ink passage in a recording head.

[Conventional technology]

Recording devices such as printers and facsimile machines can be classified into a thermal type, a wire dot type, an ink jet type, a laser beam type, and the like according to a recording method.

Also, depending on the scanning method at the time of recording, a serial type in which the recording head is mounted on the carriage and main scanning is performed in the print digit direction,
At the same time, it can be divided into a line print type for recording one line and a page print type for recording one page at a time.

The ink jet recording apparatus drives a recording head having an ejection port based on print data,
A recording medium (paper, etc.) by discharging ink droplets from the discharge port
It is configured to record an image on a computer.

The present invention relates to a recording apparatus for the above-described ink jet, and is applicable regardless of a scanning method such as a serial type, a line print type, or a page print type.

In this type of ink jet recording apparatus, a discharge unit is periodically driven (discharge of ink from a discharge port by a pressure pump or a suction pump) to release a discharge failure of a recording head.

The present inventors have repeatedly conducted many experiments. As a result, in particular, in a so-called bubble jet (BJ) type ink jet recording apparatus, since thermal energy is used as energy used for ink discharge, ink discharge may be performed depending on environmental conditions. It has been found that bubbles generated from the dissolved gas may accumulate in the recording head due to the residual heat, and if the ink ejection is repeated a certain number of times or more, the ejection may become unstable or non-ejection may occur.

As a method of driving the discharge unit, a case where a function (suction pump) for sucking ink from the ejection port side on the front surface of the recording head is provided, and a case where a pressure function (pressure pump) is provided in an ink supply path to the head. It has been known.

[Problems to be solved by the invention]

By the way, the driving of the discharge unit in the conventional ink jet recording apparatus has been performed at regular time intervals set for each recording apparatus.

However, in such a method of driving the discharging means at regular intervals, since the amount of bubbles in the recording head depends on the number of ejections of ink droplets, for example, the driving interval is determined by the amount of bubbles accumulated during solid printing. If it is determined, ink is discharged more than necessary in the case of performing normal printing with a large number of white backgrounds, and there is a problem that the printing speed is reduced and the ink consumption is increased.

An object of the present invention is to solve the problem of ejection instability and non-ejection caused by bubbles accumulated inside a print head due to repetition of a printing operation, and to perform an ink discharging operation in accordance with a change in a state in which a printing operation is repeated. It is an object of the present invention to provide an ink jet recording apparatus capable of appropriately determining the timing of performing the printing, preventing a reduction in printing speed, and eliminating wasteful consumption of ink.

[Means for solving the problem]

The present invention is directed to an ink jet recording apparatus that forms a recording image on a recording medium by driving a heater provided on a recording head based on print data to discharge ink droplets from discharge ports of the recording head. Based on the data, counting the number of data that causes ink ejection, counting the number of consecutive data that causes ink ejection, or a first predetermined value in the case of data that causes ink ejection. Counting means for performing either addition and counting for subtracting a second predetermined value in the case of data that does not eject ink, and ejecting ink from the ejection port of the recording head by suction or pressure. Discharging means, and control means for causing the discharging means to discharge ink at a predetermined timing when a count value of the counting means exceeds a predetermined value. The ink jet recording apparatus according to claim is intended to achieve the above object.

〔Example〕

 Hereinafter, the present invention will be specifically described with reference to the drawings.

FIG. 1 is a perspective view of a main part of an ink jet recording apparatus embodying the present invention.

In FIG. 1, 1 ぱ chassis (frame) of the recording apparatus
2, a recording head (ink-jet head) having a discharge port for ejecting ink droplets on the front surface, 3 a carriage on which the recording head is mounted, 4 a rail for guiding the carriage, and 5 a guide for guiding and supporting the carriage. A shaft, 6 a paper feed roller (conveyance roller), 7 a pinch roller, 8 a flexible cable connecting the main body substrate and a circuit on the carriage, 9 an ink from the ink tank on the apparatus main body side to the recording head. Supply tubes, 10
Denotes a suction pump for sucking ink from each of the ejection ports on the front face of the recording head capped (sealed).

The recording head 2 is provided with, for example, 128 ejection ports arranged vertically, and in the case of a bubble jet type, is provided with 128 ink jet nozzles each of which has a front end opening.

The carriage 3 is supported by a rail 4 and a guide shaft 5 so as to be able to reciprocate in the print digit direction. The recording head 2 is scanned by the movement of the carriage 3.

The paper feed roller 6 and the pinch roller 7 transport the recording sheet in the vertical direction.

The flexible cable 8 transmits a signal for controlling the recording head 2, and the ink supply tube 9 supplies ink to the recording head 2.

The suction pump 10 is for sucking ink from the ejection port on the front surface of the recording head 2, and is disposed at a position (home position) out of the recording range of the carriage 3 (home position) so as to be capable of closely contacting (capping) with the recording head. ing.

In this way, ink is supplied to the recording head 2 having the ejection ports, and the energy generation means for ejecting the ink provided on the recording head 2 is driven based on the print data, whereby the ink droplets are ejected from the ejection. Discharge and print medium (recording medium such as paper or plastic thin plate)
An ink jet recording apparatus for forming a recorded image on a recording medium is constructed.

However, the ink jet recording apparatus according to the present invention includes means for receiving print data transferred from a host computer or the like, means for measuring the number of print dots or the distribution of print dots in the received print data, and Discharging means for discharging more ink; and means for controlling the driving of the discharging means based on the number of print dots or the distribution state of the print dots.

The control means for controlling the discharge means may control the drive interval of the discharge means based on a predetermined sequence, or may be variable.

Further, the discharging means is another means other than a heater for discharging ink.

FIG. 2 is a block diagram of a control system of the ink jet recording apparatus according to the present invention.

In FIG. 2, a recording device 11 converts image (print) data transferred from a host system 12 by a serial image interface (video interface) into
It receives using the interface circuit 13.

The interface circuit 13 converts the serially transferred print data into parallel data, for example, every 8 bits,
The data is stored in the VRAM 15 through the AM control circuit 14.

Further, the interface circuit 13 includes a circuit 13a for counting the number of print dots in the print data.

The print dots are not limited to black dots, but may be dots such as Y (yellow), M (magenta), C (cyan), clear ink, and erasing ink.

The VRAM 15 is, for example, a dynamic RAM of 64K × 8 bits, and stores print (image) data for about 200 rasters.

The VRAM control circuit 14 converts the interface circuit 13 to the VRAM 15
And data transfer from the VRAM 15 to the print data transfer circuit 16 and control the timing of data transfer.

The microprocessor 17 is the center of control of the recording device 11, and includes a ROM 18 storing a program, a RAM 19, a port 20, and a timer 21.

The microprocessor 17 calculates the total number Nb of print dots (dots formed by ink ejection) printed using the RAM 19.
Is stored.

The microprocessor 17 controls the interface circuit 13, the print head control circuit 22, and the print data transfer circuit 16 through a bus signal line, and controls the print mechanism unit 23 using the port 20.

The print head control circuit 22 copies the print data stored in the shift register 24 in the head 2 to the latch 25 by the latch signal L1, and drives the head 2 through the head driver 26 by the drive signals HEO to HE3 in a time division manner. I do.

The print data transfer circuit 16 reads, for example, 128 bits of print data stored in the VRAM 15 in the vertical direction, and transfers the read data to the shift register 24 in the head 2. 128 data
The bit is the number 12 of the dot forming elements (printing elements) of the head 2, that is, the number of energy generating means 27 for ejecting ink.
8 is supported.

The microprocessor 17 controls the printing mechanism 23 via the port 20.

The printing mechanism unit 23 includes a recording medium feed (transport) motor, a carriage motor, a discharge unit drive motor, and the like.

FIG. 3 is a flowchart showing the operation of the ink jet recording apparatus according to the present invention having the control system of FIG.

In FIG. 3, when the printing operation is started, the step
In step 101, one raster image data is received, and in step 102
The number of print dots in the image data is
Count by a, and add that value to the total number of print dots Nb.

Next, at step 103, it is determined whether or not the image data has been received for 128 rasters (the number of rasters corresponding to the number of discharge ports of the print head).

If it has not been received yet, it returns to step 101 and repeats the above operation. If it has received it, it proceeds to step 104 and moves the carriage 3 to scan while moving.
At 105, the print data is transferred to the recording head 2, and at step 106, the dot forming element of the recording head 2 is driven to form a recording image on a recording medium such as paper.

In step 107, it is determined whether or not printing for one line has been completed. If not, the process returns to step 104 and the above operations are repeated.

If printing of one line has been completed in step 107, the process proceeds to step 108, where it is determined whether or not the total number Nb of print dots has reached the number Np that requires ink discharge from the ejection openings.

If the number of print dots reaches the set value Np, go to step 10
In step 9, the carriage 3 is moved to the home position. In step 110, the ejection means is driven (ink is ejected from each ejection port and ejected). In step 111, the number of print dots (counter value) Nb is reset to 0. Then, the recording medium is fed in step 112, and it is determined in step 113 whether printing for one page has been completed.

If the total number of print dots Nb does not exceed the set value Np in step 108, the process jumps to step 112 to feed the recording medium, and proceeds to step 113.

If printing for one page has been completed in step 113, the printing operation is terminated. If printing for one page has not been completed yet, the flow returns to step 101 and the above steps are repeated again.

FIG. 4 shows the configuration of a print density evaluation circuit incorporated in the interface circuit 13 of the control system in another embodiment of the ink jet recording apparatus according to the present invention.

The print density evaluation circuit shown in FIG. 4 includes an up-down counter 31, a comparator 32, a D flip-flop 33, and an output buffer.

In FIG. 4, image data from the host system 12 (FIG. 2) is a signal VDO of image data and a cloak signal V.
Sent by DOCK.

In the case of black printing, the up / down counter 31 counts up when the image data is black, and counts down when the image data is not printed (white background). Therefore, the count value increases as print dots continue.

The comparator 32 compares the output value of the counter 31 with the output value of the D flip-flop 33. D flip-flop 33
When the output value of the counter 31 is larger than its own value,
The output value of the counter 31 is stored.

Therefore, the D flip-flop 33 stores the maximum value of the output of the counter 31 during one raster.

The output value of the D flip-flop 33 is read out to the microprocessor 17 through the output buffer 34.

 The signal OE is an output control signal of the output buffer 34.

According to the ink jet recording apparatus provided with the print density evaluation circuit of FIG.
The number of print dots is measured by, and the discharge means is driven when the measured value reaches the set value. The means is driven.

Therefore, in this embodiment, when the number of print dots is large and the print dots are distributed with a certain degree of concentration, the discharge dots are detected and discharged earlier, otherwise the discharge interval is long. Is done.

In this manner, an ink jet recording apparatus capable of preventing a reduction in printing speed and preventing wasteful consumption of ink is obtained.

As a method of discharging ink from the discharge port, in addition to the method of sucking ink from the front surface of the head with a suction pump as in each of the above-described embodiments, a pressing mechanism (pressurizing) is provided in the ink supply path to the head 2. A method of providing ink under pressure by providing a pump or the like is also possible.

FIG. 5 is a flowchart of a recording operation for determining the drive interval of the discharging means in accordance with the degree of concentration of the number of print dots using the interface circuit of FIG.

In FIG. 5, when the printing operation is started, the step
In step 201, image data for one raster is received.
In step (1), the number of print dots in the image data is counted by the counter 13a, and the value is added to the total number of print dots Nb.

Next, in step 203, the correction value by the print density evaluation circuit as shown in FIG. 4 is added to the total number Nb, and in step 204, the image data is converted into the raster number corresponding to the dot forming element (ink ejection port) of the head 2. It is determined whether or not (for example, 128 rasters) has been received.

If the data for the number of rasters has not been received yet, the process returns to step 201 and the above steps are repeated.

If data for the number of rasters has been received, step 205
In step 206, the print data is transferred to the print head 2 while the carriage 3 is moved and scanned.
In step 207, the dot forming element of the print head 2, that is, the energy generating means for discharging ink is driven to form (record) an image on the recording medium.

In step 208, it is determined whether or not printing for one line has been completed. If not, the process returns to step 205 and repeats the above-described printing operation. When printing for one line has been completed, the process proceeds to step 209 to perform printing. It is determined whether or not the total number Nb of dots has reached the number Np that requires discharge of ink from the ejection openings.

When the number of print dots reaches Np, the carriage 3 is moved to the home position in step 210, and the drive of the discharging means is performed in step 211. Operation such as pressurizing and ejecting the ink), and resetting the number of print dots (counter value) Nb to 0 in step 212,
In step 213, sheet feeding is performed, and in step 214, it is determined whether printing of one page has been completed.

If the number Nb of print dots has not reached the set value Np in step 209, the process jumps to step 213 to feed a recording medium (paper or the like), and proceeds to step 214.

If the printing of one page is completed in step 214, the printing operation is terminated.
Return to 201 and repeat the above steps again.

FIG. 6 is a block diagram showing another example of the configuration of the print density evaluation circuit provided in the interface circuit 13 in FIG. 2, which is different from FIG.

In FIG. 6, 41 is an addition constant, 42 is a subtraction constant,
Reference numeral 43 denotes a selector, 44 denotes an adder (adder), 45 denotes a D flip-flop, 46 denotes a comparator, 47 denotes a D flip-flop, and 48 denotes an output buffer.

The selector 43 is an addition constant when image data is printed.
The set value + N of 41 is selected, and the set value -M of the subtraction constant 42 is selected for non-printing.

Therefore, the value of the D flip-flop 45 is
The count is + N per piece and -M per non-printing. These set values + N, -M are set to, for example, +3, -2, etc., but can be changed by a register, a switch, or the like.

Therefore, the relationship between the continuity of the printing dots and the degree of increase / decrease of the D flip-flop 45 can be freely set.

The comparator 46 and the D flip-flop 47 in FIG.
The functions of the output buffer 48 and the like are the same as those of the comparator 3 in FIG.
2. The functions are substantially the same as those of the D flip-flop 33 and the output buffer 34.

In this case, regarding the degree of concentration of the print dots, when print data is expanded in the horizontal direction as a dot image and serially received, the register is + N for print dots and −
If the maximum value of the register in one raster exceeds a certain value, it is determined that the number of dots is concentrated.

As described above, the present invention evaluates the number and concentration of print dots in print data in a printing apparatus, and determines a drive interval of a discharge unit for removing bubbles in ink based on the evaluation. Therefore, it is possible to control such that the drive interval is always optimized, and to obtain an ink jet recording apparatus capable of preventing a decrease in the printing speed and minimizing the ink consumption.

〔The invention's effect〕

As is apparent from the above description, according to the configuration of the present invention, a value relating to data for causing ink to be ejected in the print data is counted, and suction or suction is performed on condition that the counted value exceeds a predetermined value. The timing for performing a discharge operation of discharging ink from the discharge port of the recording head by pressurization is determined.

According to the present invention, an ink discharging operation is performed in response to a change in a state in which a printing operation is repeated in response to an unstable ejection or a non-ejection caused by bubbles accumulated in a print head due to repetition of a printing operation. It is possible to obtain an ink jet recording apparatus in which the timing can be appropriately determined, the printing speed can be prevented from lowering, and the ink is not wasted.

[Brief description of the drawings]

1 is a perspective view of a main part of an ink jet recording apparatus embodying the present invention, FIG. 2 is a block diagram of a control system of the recording apparatus of FIG. 1, FIG. 3 is a flowchart of an operation of the control system of FIG. FIG. 4 is a block diagram of a print density evaluation circuit in another embodiment of the present invention, FIG. 5 is a flowchart of a recording operation of an ink jet recording apparatus using the evaluation circuit of FIG. 4,
FIG. 6 is a block diagram of a print density evaluation circuit according to still another embodiment of the present invention. 2 ... print head, 3 ... carriage, 9 ... ink supply tube, 10 ... discharge means (suction pump), 13 ... interface circuit, 13a ... print dot counter, 19a
... Print dot total (Nb) storage unit 31, up-down counter, 41 addition constant (+ N), 42 subtraction constant (−M).

Continuation of the front page (56) References JP-A-63-252748 (JP, A) JP-A-62-248656 (JP, A) JP-A-1-281950 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) B41J 2/165

Claims (1)

(57) [Claims] An ink jet recording apparatus for forming a recorded image on a recording medium by driving a heater provided in the recording head based on print data to discharge ink droplets from a discharge port of the recording head. Based on the print data, counting the number of data that causes ink to be ejected, counting the number of consecutive data that causes ink to be ejected, or a first predetermined value in the case of data that causes ink to be ejected A counter for subtracting a second predetermined value in the case of data that does not cause ink ejection to be added,
A discharging means for discharging ink from the discharge port of the recording head by suction or pressurization; and when the count value of the counting means exceeds a predetermined value, the discharging is performed at a predetermined timing. An ink jet recording apparatus comprising: control means for causing ink to be discharged by means.